Increased pre-dispersal seed predation in sunflower crop-wild hybrids

The fitness of crop-wild hybrids can influence gene flow between crop and w ild populations. Seed predation levels in crop-wild hybrid plants can be an important factor in determining plant fitness, especially in large-seeded crops such as sunflower. To determine patterns of pre-dispersal seed predat ion, seeds were collected from wild sunflowers (Helianthus annuus L.) and w ildxcrop F-1 hybrids at three experimental field sites in eastern Kansas. S eed heads were dissected and each seed was counted and scored for categorie s of seed damage by lepidopteran and coleopteran larvae. Hybrid seed heads showed significantly higher levels of insect-damaged seeds. The average hyb rid plant had 36.5% of its seeds (or 45.1 seeds per plant) eaten by insect larvae while the average wild plant lost only 1.8% (or 95 seeds) to seed pr edators. Hybrid populations had higher levels of total insect damage even w hen date of flowering, flower head diameter, and the number of open heads w ithin the study site were accounted for. These results suggest that the red uced fecundity of F-1 crop-wild sunflower hybrids demonstrated in other stu dies may be augmented by the increased seed predation in hybrid flower head s. Fecundity estimates of crop-wild hybrid and wild plants that disregard d ifferential seed predation levels may not accurately reflect the actual rel ative contributions of hybrid and wild plants to future generations.